Joining two object in Blender
Ronin, 

I've taken a look at the model, you have a simple vertice problem which is solved like this:

Select vertice 1 and then select vertice 2


Hit Alt + M and select "At Last" to merge at the second vertice


Do this for both of these, and your problem should be solved


I would also recommend deleting these faces as they are only taking up vertice count and can potentially mess up the model.


Before


After